Gabriele Albin had known for a long time that she would have one final meeting with her "friend" at Dusseldorf's courthouse but when it came, the encounter still caught her off guard. It was as she was walking towards the canteen during a recess that she heard the familiar voice from behind. "Hello, Gabriele," the middle-aged woman whispered. Ms Albin swung around, fixed her eyes on "Vera Wagner's" sheepish face, and then began to scream.

"Leave me alone ... Go away ... You have ruined my life," she shouted. "Vera" drew back, heads turned in the echoing corridor, the man from the Stasi a few paces behind stopped in his tracks, and Ms Albin's legs gave way. "I can't bear this any longer," she sobbed. "I am on trial while these people are free, paraded as witnesses against me. It's so unjust."

The justice of it all is for the court to determine. Ms Albin is charged with treason, for betraying Nato military secrets to the East German security agency, the Stasi. But if she is convicted, it will be with the help of testimonies obtained from full-time Stasi operatives who ensnared her in the 1980s and who themselves are immune from prosecution. All Stasi personnel dealing with foreign espionage but based in the former East Germany have been given an amnesty, with full pension rights. Some are even working for united Germany's spy service, the BND. "Vera Wagner" - real name Edeltraut Richter - and Heinz Keller, the Stasi controller, are untouchable but obliged by law to provide evidence against the people they had once manipulated.

Ms Albin, who may be sentenced to a long prison term today, is not so fortunate. She seems to have had a sad life with many bad breaks, probably none worse than that fateful love affair in the summer of 1977 with the handsome man who introduced himself as Frank Dietzel. His real name, as she discovered many years later, was Rudolf Reck. He was something of an East German James Bond, a skillful exponent of what is referred to in the trade jargon as "the Romeo method".

A military translator at the US embassy in Bonn, Ms Albin fell head over heels in love. They got engaged, though Reck was away most of the time, his absences attributed to business in Saudi Arabia. He also claimed to be working for a peace foundation; the cover he used to persuade his "fiancee" to steal military documents from the embassy. "Looking back on all of this now, almost 20 years later, I was a terribly naive fool," she admits.

The relationship ended in 1984, after a row at a restaurant in the Austrian ski resort of Innsbruck. In 1986 Ms Albin married another man, and Reck vanished from the scene. But the marriage broke down a year later, along with her nerves, and Reck miraculously reappeared to console her. He even introduced her to "Vera", a warm, charming woman who also happened to work for the "peace foundation".

And so Ms Albin resumed her pilfering at the embassy, with "Vera" as the conduit of the stolen documents. The defence states this link soon fizzled out, but the prosecution maintains Ms Albin continued to work for the Stasi until shortly before she quit her job at the embassy in early 1990.

She was arrested in 1991 and charged with espionage, her guilt established by the extensive files discovered at the Stasi headquarters after the fall of the Wall. For five years she has had to report to the authorities every week as the state prepared its case. Now, several nervous breakdowns later and after a flurry of expert testimonies stating that Ms Albin is unfit to stand trial, she is finally in the dock.

From the state's point of view, the delay made sense. The amnesty only came into effect at the end of last year, which is exactly when the wheels of justice began to turn in earnest. But the key witness, Reck the Romeo, will not be able to honour the court with his presence. He died in an unexplained car accident last year, driving directly into the path of a train.

Step forward Herr Keller, the man to whom Reck reported in East Berlin, and "Vera Wagner". The accounts of the defence and prosecution diverge on the question of what motivated Ms Albin to betray her country, and the court seems eager to find evidence of greed. There is little doubt that Ms Albin was emotionally under Reck's control, but the prosecution maintains she was paid money for services rendered. "A fee was paid," confirmed Mr Keller, though he "could not remember" the sums involved, to the obvious displeasure of the public prosecutor, a tenacious woman with a sharp tongue. Nor could he be sure whether the money reached Ms Albin, who claims she did not receive it, or was pocketed by Reck.

Mr Keller, a man with a distinguished head of grey hair and healthy tan, was clearly uncomfortable with his role, casting nervous sideway glances at the defence bench. He was controller of "Source Gerhard", the code name for the Stasi agent in the US embassy. "How secret were the documents obtained from Source Gerhard?" he was asked. "They were marked confidential," he replied.

"Highly confidential?"

"Perhaps".

"Top Secret?"

"No."

The prosecutor probed further: "Were there any plans for Nato military exercises among them?"

"No," Mr Keller said.

Oops, the German state's counter-espionage effort had just suffered a setback. The charge sheet specifically accuses Ms Albin of removing documents detailing Nato manoeuvres, such as "Operation Flintlock". They also equate her with "Source Gerhard", about which there appears to be some doubt. Ms Albin says she is "credited" with removing documents she never saw, and wonders whether there might have been a "second man or woman" operating under the codename.

Mr Keller testified that the Stasi had applied meticulous sex discrimination and never used a male codename for a female operator, or vice versa.

"Except in this case," the judge suggested.

"Except in this case," Mr Keller concurred.

"Vera" turned out to be of little use at the trial, so yet more retired Stasi agents were wheeled out. So far, none of them has been able to link Ms Albin directly with the hottest documents on display. Several testified that Ms Albin could not have known she was working for the Stasi. Apparently, a previous attempt to dupe her failed when she went directly to her US superiors to report a suspicious incident.

Maybe there is another Gerhard out there, and maybe Ms Albin was not quite the Mata Hari she is alleged to be. It is even conceivable that bringing all those Stasi agents from their retirement cottages in eastern Germany to Dusseldorf has been a complete waste of the German taxpayers' money, and that Ms Albin's tribulations a decade after her crimes and six years after the collapse of the Warsaw Pact might not advance the cause of justice all that much.